Caroline, Section 508 is the US regulation governing accessibilty
for government sites.
<p>
From <a href="
http://www.section508.gov/">
http://www.section508.gov/</a>
<blockquote>
Section 508 requires that Federal agencies' electronic and
information technology is accessible to people with disabilities.
</blockquote>
<p>
You can check if a page meets section 508 guidelines at
<a href="
http://bobby.watchfire.com/bobby/html/en/index.jsp">
http://bobby.watchfire.com/bobby/html/en/index.jsp</a>
although the short answer is that almost none in OpenACS do right now.